Method of and means for preparing magnetizable bodies to receive and retain magnetic impressions



0. WEITMANN ET AL Filed Oct. 24, 1940 TO RECEIVE AND RETAIN MAGNETIC IMPRESSIONS July 7, 1942.

mmnon OF AND MEANS FOR PREPARING A MAGNETIZABLE BODY mwmnnunl mn munnnnnnnmz Xgg TO R 5 WAX-W ATTORNEY Patented July 7, 1942 METHOD OF AND MEANS FOR PREPARING MAGNETIZABLE BODIES TO RECEIVE AND RETAIN MAGNETIC IDIPRESSIONS Otto Weitmann, Binghamton, and John B. Sponsler, Vestal, N. Y., assignors to International Business Machines Corporation, New York, N. Y., a corporation of New York Application October 24, 1940, Serial No. 382,594

2 Claims. (Cl. 179-10) This invention relates to a new and improved method of and means for preparing a magnetizable body to receive and retain magnetic impressions.

It is well known to those skilled in the magnetic recording art, that it is necessary to remove previous recordings or impressions from the mag netizable bodies, such as magnetic paper tapes, steel tapes, magnetic statistical cards, etc. upon which it is desired to record, by magnetically erasing or obliterating the said recordings or impressions; and that it is also necessary to condition the magnetizable body so that before recording operations are eifected, the magnetic sensitivity of each sheet, tape, or card is restored to a maximum and consistent state.

It is accordingly an object of the present invention to provide a new and improved method of and means for obliterating or erasing magnetic effects or impressions retained upon magnetizable bodies.

It is recognized by applicants that several methods of preparing and recording are employed in the art. One method comprises erasing all previous magnetization on the body by subjecting it to an alternating magnetic field and reducing its magnetic condition to a zero magnetic level or state, then'during recording operations impressing a constant polarizing field upon the body and superimposing thereupon varying signal strengths. Another method comprises erasing all previous impressions on the body by subjecting it to a unidirectional polarizing field to saturate fully the magnetizable body, and then impressing the magnetic recordings thereon. This method is the reverse of the former in that the body is magnetized and the impressions are erased from it, while in the former case all magnetizations are erased and impressions are recorded on thereon.

It will be seen that the present invention is applicable to any preferred method of recording in that the magnetizable body is restored to the normal zero magnetic condition. If, in addition thereto, it is desired to impress thereupon a constant polarizing field to saturate the zeroized body, this step can be eifected by subjecting the body to a suitable polarizing field upon its departure from the instant device. This latter step is not deemed pertinent to the present invention.

In addition to recording and reproducing sound magnetically, it has been suggested to employ individual magnetizable sheets as statistical machine control records. The discrete and differentially disposed magnetized areas retained by these sheets represent the different data and facts which are to be compiled by the computing or accounting units of the machines. Now, in order to record diflerent data upon the said control records, which are referred to in the art as tabulating cards, it is necessary to provide means capable of obliterating satisfactorily the previous discrete magnetizations retained by these cards, and capable of conditioning the cards in order to be suitable for receiving the new magnetic data recordings thereon. It is accordingly an object of the present invention to provide means capable not only of conditioning sound receiving records, but also of obliterating discrete magnetic impressions from individual statistical records, and thereby conditioning these records for data recording operations,

To attain this end, it has been established by experiment that the said statistical records are conditioned properly and rendered devoid of any previous magnetic impressions if they are subjected progressively to varying magnetic fields of different polarities. The instant device comprises a pair of suitably spaced'electromagnets, which are so connected that, when an alternating current supply is impressed thereupon, individual positive and negative magnetic fields are produced simultaneously at periodic intervals. The magnetized records are fed continuously through the opposing and varying magnetic fields so as to be subjected first to the action of one polar field, and immediately thereafter subjected to the action of the second polar field. Due to the continuous motion of the records through the magnetic fields, and due to the varying intensities of the fields, it is understood that each individual record is subjected to varying flux densities as it progresses through the mentioned magnetic fields. The path traversed by the records through the said fields is an arcuate one, so'that the linking lines of force between the magnetic poles traverse the records at approximately right angles at the points opposite the pole pieces of the electromagnets.

Accordingly, another object of the present invention resides in the provision of a method of and means for subjecting the magnetized records to varying magnetic fields of opposite polarities by feeding the records individually in an arcuate path through the said fields.

It is recognized that obliterating methods and means have been suggested heretofore, whereby the records are fed through varying magnetic fields. Such devices are described in the U. S.

Patents Nos. 1,459,202, 1,828,190 and 2,210,770. However, up to this time, no provision has been made, as disclosed herein, for feeding the records in an arcuate path through opposite magnetic fields whereby the linking lines of force are impressed upon the records at substantially right angles.

Other objects of the invention will be pointed out in the following description and claims and. illustrated in the accompanying drawing, which discloses, by way of example, the principle of the invention. and the best mode which has been contemplated of applying that principle.

In the drawing:

Fig. 1 is a side elevational view of the obliterating apparatus shown in connection with suitable sheet feeding means.

Fig. 2 is a plan view of the obliterating apparatus shown in Fig. 1.

Fig. 3 is a wiring diagram showing the control circuit for the sheet feeding means.

Referring now to Figs. 1 and 2 a preferred embodiment of the present invention is shown, which has been used eifectively for erasing discrete magnetic areas or impressions retained by magnetizable steel tapes, ferro-magnetic powdered tapes, ferromagnetic powdered paper tabulating cardsletc'. The obliterating device comprises the spaced electromagnets l and II which are supported by, and linked together magnetically by yoke l2 of suitable material, such as soft iron. The windings of the said electromagnets are connected in parallel circuit arrangement by conductors l3, which conductors, in turn, are connected to a suitable alternating current supply designated generally by the reference character H. The windings of the electromagnets I0 and H are arranged so that with the described connections the directions of current flow are opposite to produce opposing magnetic fields, or stated in other words, for producing flux densities which are of opposite polarity. Thus, for example, it will be understood that, at an instant, the fiux density at a is comparatively weak,-being the stray flux from magnetic pole S and is negative; and that at the point b the flux attains a maximum negative value; and decreases to zero value at point e where the influence of the positive flux from pole N is equal to the influence of the negative flux from pole S; and at point (1 attains a maximum positive value; and atpoint e decreases to a relatively low positive value.

In order to feed the sections of the magnetized bodies, such as tapes or cards, progressively through the varying magnetic fields of opposite polarity, just referred to, in an arcuate path, a suitable curved guide slot I5 is provided in the member IS. The said member consists of suitable non-magnetic material, such as brass, and can be formed so that the arcuate path formed by the guide slot is totally or partially enclosed.

It is understood that the guide slot is curved in the direction indicated in Fig. 1, so as to cause the linking flux between the pole pieces of the. electromagnets to be impressed upon the magnetic bodies fed therethrough at substantially right angles at points b and d.

The pole faces of electromagnets l0 and II should approximately be at least 25% wider than the width of the magnetic bodies Passed thereover so that lateral fluctuations of the magnetizable body do not destroy the homogeneity of the leakage field. The magnetic sensitivity characteristic of the said body as it leaves the varying magnetic fields is therefore substantially constant in spite of any lateral fluctuations thereof occurring during the feeding of the body through the guide slot.

The values of the flux density of each pole of the electromagnets should be sumcient to saturate the magnetic body at points b and d. For example, in an actual application, the recording flux value used was 70,000 lines per square inch, this value being used for recording discrete magnetic impressions upon ferro-magnetic powdered paper tapes. It was determined, by experiment, that a flux value equivalent to 1500 lines per square inch was satisfactory to obliterate such magnetic recordings. However, a value oflapproximately 1800 lines per square inch was found necessary to saturate magnetically the tape in question. Consequently, in this instance the flux value for each pole of the said electromagnets was made in excess of 1800 lines per square inch.

It has been found that the magnetizable bodies could be fed manually through the arcuate path so that individual sections thereof are positioned progressively through the varying magnetic fields. It is evident too, that any suitable feeding means for such tapes or sheets could be employed to feed continuously these bodies through the said fields.

For example, in Fig. 1, a well known type of feeding device for statistical cards is shown,

whereby the individual cards are fed longitudibeing returned by a spring 25 when the solenoid is deenergized. Suitable constantly rotating feed rolls 26 and 21 are provided and disposed so that the first mentioned rolls advance the cards fed from the magazine through the guide slot, so that the leading edges thereof are engaged by the latter rolls upon their departure from the obliterating device. A suitable receiving pocket 28 is provided and suitably disposed with respect to feed rolls 21. A well known type of pivoted card lever 29 isdisposed in the path of the cards at the feed rolls 21 so that as the cards pass this point the lever is partially rotated in a counterclockwise direction to open the associated contacts 30. These contacts control the energize,- tion and deenergization of solenoid 24. By referring to Fig. 3, it is seen that the said contacts are connected in series with the feed control solenoid and battery 3|. Thus, upon closure of the control switch 32, and assuming that no cards have been fed from the magazine, due to the normal closed position of contacts 30, the solenoid 24 is energized to effect feeding of the cards. until the leading edge of the first card engages the card lever 29 to cause the associated contacts 30 to open, whereupon the solenoid is deenergized. Subsequent energizations thereof occur when the trailing edges of the cards leave The said solenoid remains energized the invention as applied to a single modification,

it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. Apparatus for preparing a magnetizable body for receiving and retaining magnetic impressions comprising a plurality of spaced electromagnet means for producing magnetic fields of opposite polarity, and an arcuate guide member disposed in close proximity to the spaced electromagnets and extending longitudinally thereof for guiding the magnetizable body through the said magnetic fields.

2. The invention set forth in claim 1 characterized by the fact that the said arcuate guide member is shaped so that the linking lines of force of the magnetic poles formed by the said electromagnets traverse the magnetizable body at substantially right angles at the magnetic poles.

O'I'I'O WEITMANN. JOHN B. SPQNSLER. 

